BRUSSELS (Reuters) - Four
months ago, Jean-Claude Juncker would have struggled to
have his name recognized in much of Europe. Now he could
be forgiven for wishing people would shut up about him.

As the top candidate of Europe's largest center-right political
group, which won the European elections last month, the former prime
minister of Luxembourg is in pole position to become the next
president of the European Commission.

While Britain's David Cameron is adamantly opposed and The Sun
tabloid has described him as "The Most Dangerous Man in Europe",
Juncker remains on track to secure the powerful post, which has
influence over policy from telecommunications to banking and trade
affecting 500 million Europeans.

Cameron's opposition is based on a belief that Juncker, 59, is an
"old-school federalist" wedded to the concept of "ever closer
union", not a modernizer who will shake up and refocus Brussels
institutions regarded in London as bloated and opaque.

After an election in which millions of Europeans voted for far-right
or protest parties, with resentment widespread over immigration,
unemployment and low growth, Cameron is determined to force a
rethink about how the Commission works.

German Chancellor Angela Merkel and most EU leaders agree that
sharper priorities need to be set for the Commission, whose 25,000
civil servants have seen their responsibilities grow from mostly
economics, trade and agriculture into areas such as culture and
education, health and foreign affairs.

While Merkel has given resolute backing to Juncker, saying he is the
right person to lead the Commission for the next five years and
ensure it delivers on jobs, growth and prosperity, Cameron takes the
polar opposite view.

The question, then, is whether the heavy smoking deal broker who got
his first ministerial job at 29 is the best choice at a time when
Europe is battling to keep its economic recovery on track, faces
geopolitical tension with Russia and is confronting rising social
and political opposition to "more Europe".

And whether, as the 12th president of the Commission since the post
was established in 1958, Juncker would represent continuity or a
break with the past.

POLITICAL FIXER

Unlike some of the EU's founding fathers, Juncker has never set out
his own doctrine of European integration.

The son of a Luxembourg steelworker who often says he would never
have been able to study law and get ahead if his father had not had
job security, Juncker stands somewhat to the left of the EU's
center-right mainstream.

For example, he supports a minimum wage in all EU countries.

But his record is more that of a practical operator, making the EU
plumbing work by brokering crucial compromises between Germany and
France on economic and monetary union.

He negotiated the bloc's original budget rules in the 1997 Stability
and Growth Pact and an amended rulebook in 2005 after Berlin and
Paris broke the deficit limits and froze the pact.

For most of the euro zone debt crisis - perhaps the biggest
challenge the EU has faced since its founding in the 1950s - he was
at the heart of decision-making.

As chairman of the euro zone's finance ministers and a prime
minister, he lead negotiations or sat in every critical meeting from
the first word of Greece's problems in 2009 to the concluding
decisions on banking union in 2013.

It was exhausting work and took a toll on his health. Critics said
his chairmanship was at times erratic and decisions sometimes lacked
follow-up.

His Dutch successor criticized his drinking and smoking in meetings.
Juncker denied any alcohol problem.

At the peak of the crisis in 2011, he grew frustrated with the media
attention, confessing he preferred "secret, dark debates" to the
bright lights of news conferences.

In an effort to stop leaks at one meeting of finance officials in
Luxembourg, a Grand Duchy of just 500,000 people that he governed
for 19 years until July 2013, Juncker warned participants that their
telephones could be monitored.

To some critics, his approach suggested a man concerned more to do
whatever it takes to get a deal than with the niceties of openness
and modern government.

Former staff members describe him as liking nothing more than
locking himself in his study to work the phones, and say he only
ever wants one or two trusted people around him.

"He's old-fashioned and a bit secretive in the way he works," says
one former adviser. "He doesn't even like the idea of having a
cabinet," he said, using the French term for a private office staff.
"It's not something he was to used in Luxembourg."

By contrast, running the European Commission entails having a team
of up to 25 advisers to handle a host of policy portfolios, not a
one-man job. The president must also travel widely and make several
speeches a week, something Juncker is loath to do unless he has
penned them himself.

"He hates giving speeches he hasn't written," said the former
staffer. "There are a lot of things you are forced to do as
Commission president that are not really up his street."

In his manifesto, Juncker pushed all the right buttons, talking
about jobs, growth, energy diversification and trade, as well as the
need to further reform Europe's monetary union.

But when he outlined how he sees the relationship between the
Commission and the European Central Bank, and how he would handle
future financial rescues, he raised some warning flags.

In the fourth point of his five-point plan, he praised ECB President
Mario Draghi for helping save the euro, before adding that the euro
zone should be managed by the Commission, which should also have a
say in exchange-rate policy.

"The responsibility of the Eurogroup includes issues related to the
exchange rate. We should not forget this in case the euro exchange
rate should increase further and become a problem for growth," the
manifesto says.

The EU's governing treaty allows euro zone finance ministers to set
exchange rate policy guidelines for the central bank at the
Commission's recommendation, but in practice the euro has floated
freely since its creation and monetary policy is the sole preserve
of the ECB.

Juncker's position could be seen by some as unhealthy meddling in
free markets.

He also argued that future bailout programs should go through a
"social impact assessment" not just a fiscal analysis.

That may cheer voters in Greece, Portugal and Spain who were angered
by austerity conditions attached to their bailouts. But it pits
Juncker against Merkel and others who argue it was right to set
strict terms for financial help.

The manifesto also talked of a "targeted fiscal capacity" for the
euro zone - a nod to some sort of shared budget or fiscal transfers
that Cameron and other north Europeans are concerned would take
Europe in the wrong direction.

"It's just not where we see Europe going," says a British diplomat.
"His philosophy is outdated. It's out of touch."

Juncker has in the past supported the idea of euro zone bonds - the
issuance of jointly guaranteed debt by euro zone governments - an
idea that Merkel strongly opposes. He backed away from that during
the campaign, saying conditions will not be ripe in the next five
years.

His commitment to the EU treaty goal of "ever closer union",
especially among the 18 countries that share the euro, worries those
outside the currency area as it could cement a two-tier EU,
exacerbating tensions between the "ins" and "outs".

OUT OF STEP?

While Juncker's principles may put him at odds with Cameron, they
are not out of step with past Commission presidents such as France's
Jacques Delors or Italy's Romano Prodi, who made the case
passionately for more Europe.

But after the existential crisis of the past four years and last
month's vote, Cameron and his allies argue there can be no "business
as usual". Another Commission president in the same mould - the
third from Luxembourg - is not the way to enact change, they
contend.

Added to that, Juncker clashed bitterly with Britain in 2005 over
the EU budget, leaving resentment on both sides.

As a result, Cameron has made clear he will do what he can to stop
Juncker, and he may yet succeed.

Sweden, Hungary and the Netherlands largely agree that the
Luxembourger is not the right person to modernize the Commission. If
Italy were to lean Cameron's way, it might convince Merkel that
Juncker's candidacy is not going to work.

EU leaders will meet on June 26-27 to discuss the issue, but it is
unlikely to be resolved by then. Instead, it may not be until
September or October that the fate of Juncker, and with it the
future direction of the EU, is determined.